With bushy beards and funky blue, yellow or brown faces, guenon monkeys have some of the most colorful and quirky faces of all primates. A close study of more than 20 guenon monkey species reveals these sociable animals may rely on their distinctive patterns to prevent interbreeding.

"Animals use coloration and patterning for a whole host of different reasons, and we think guenons are using their patterns to recognize different species," said study lead author William Allen, of the University of Hull in the United Kingdom.